The director-general of Queensland's Transport and Main Roads Department has stood aside while he is investigated over claims that he misled State Parliament.

Michael Caltabiano has been referred to the Ethics Committee after Transport Minister Scott Emerson wrote to the Speaker seeking an examination of Mr Caltabiano's evidence before a recent budget estimates hearing.

Mr Caltabiano told the hearing he had no previous working relationship with departmental liaison officer Ben Gommers.

But media reports have suggested otherwise. It is alleged Mr Caltabiano is named with Mr Gommers on the register of lobbying firm Entre Vous.

In a letter to the Speaker, Mr Emerson expresses concern about the apparent business link between the two men.

Mr Emerson says he is concerned it raises a prima-facie case that Mr Caltabiano could have misinformed the committee over the matter.

"Let me say very clearly, when I asked Mr Caltabiano about the inconsistencies in the media report, he made it very clear that he had told the truth and was accurate in his statements," he said.

"However, I retained concerns about those media reports compared to his statements, as did the Premier."

The minister said he believe the matter required the appropriate scrutiny by Parliament's Ethics Committee.

Mr Caltabiano has stood aside on full pay.

Deputy director-general Neil Scales will act in the role in the meantime.

Powerbroker

He is a Liberal powerbroker and also a former state MP who was once touted as a future premier but lost his seat in 2006.

After the election in March, Premier Campbell Newman hand-picked Mr Caltabiano to become director-general of the Transport Department.

The appointment was criticised by prominent QC Tony Fitzgerald, who said "the jobs-for-the-boys gravy train has already started".

But Mr Newman defended his decision.

"He has been a political player but he is totally qualified to do this job," he said.

"The point is he will build roads, he will fix the public transport system with whoever the new minister is.

"He will deliver and I am taking this political risk by making this appointment."